1. Field of Invention
The present invention relates to a display device and a manufacturing method thereof, and more particularly, to a display device and a manufacturing method thereof including an organic semiconductor layer.
2. Description of the Related Art
A flat display device has become popular due to its advantages of light weight, slimness, etc. The flat display device includes an LCD (liquid crystal display), an OLED (organic light emitting diode), etc. The flat display device includes a thin film transistor substrate formed with a thin film transistor.
The thin film transistor controls and drives a pixel. The thin film transistor includes a semiconductor layer formed of amorphous silicon, polysilicon, an organic semiconductor or the like. Since the organic semiconductor can be formed at relatively normal temperature and pressure conditions, the organic semiconductor can reduce cost and be applied to a plastic insulation substrate to protect the plastic insulation substrate which otherwise is prone to be damaged by heat. Thus, a thin film transistor formed of the organic semiconductor has been under development as a driving element for a display device.
The organic semiconductor is relatively simply formed by an ink jetting method which does not need additional processes, such as a spin coating process, an exposing process, a developing process, etc. However, an organic semiconductor formed by the ink jetting process has a small grain size because of being insufficiently crystallized. If the grain size thereof is small, impurities such as water, etc. are trapped at a grain boundary and hinder a hole injection. Thus, an on/off property and mobility of a thin film transistor are deteriorated.